Current cellular broadcast services provided by a base station serve a group of users within a coverage area of the base station. A base station transmits the same information to all, or a group of, users. In order to guarantee that all users located within the coverage area of the base station can receive the broadcast services with a required quality of service (QoS), the base station limits the data rate of the broadcast service to a worst channel condition or a cell boundary.
The conditions of wireless channel change over time and a wireless transmit/receive unit (WTRU) experiences dramatic variations in the channel conditions due to multipath fading, path losses via distance attenuation, shadowing by obstacles or interference. Not all users are subject to the worst channel conditions. Users may have a much better channel condition than the assumed worst case.
It is possible to serve a large number of subscribers by using a high transmission power, a high channel coding rate and transmit diversity scheme. However, by limiting the data rate to the worst channel condition, the current broadcast services underutilize better channel conditions with higher channel capacity.